SREBP-1c/MicroRNA 33b Genomic Loci Control Adipocyte Differentiation

White adipose tissue (WAT) is essential for maintaining metabolic function, especially during obesity. The intronic microRNAs miR-33a and miR-33b, located within the genes encoding sterol regulatory element-binding protein 2 (SREBP-2) and SREBP-1, respectively, are transcribed in concert with their host genes and function alongside them to regulate cholesterol, fatty acid, and glucose metabolism. SREBP-1 is highly expressed in mature WAT and plays a critical role in promoting in vitro adipocyte differentiation. It is unknown whether miR-33b is induced during or involved in adipogenesis. This is in part due to loss of miR-33b in rodents, precluding in vivo assessment of the impact of miR-33b using standard mouse models. This work demonstrates that miR-33b is highly induced upon differentiation of human preadipocytes, along with SREBP-1. We further report that miR-33b is an important regulator of adipogenesis, as inhibition of miR-33b enhanced lipid droplet accumulation. Conversely, overexpression of miR-33b impaired preadipocyte proliferation and reduced lipid droplet formation and the induction of peroxisome proliferator-activated receptor γ (PPARγ) target genes during differentiation. These effects may be mediated by targeting of HMGA2, cyclin-dependent kinase 6 (CDK6), and other predicted miR-33b targets. Together, these findings demonstrate a novel role of miR-33b in the regulation of adipocyte differentiation, with important implications for the development of obesity and metabolic disease.     

Neurobiology and cellular pathogenesis of glycolipid storage diseases

Disorders of lysosomal metabolism often involve the accumulation of specific types of glycolipid, particularly gangliosides, because of either degradative failure or other currently unknown mechanisms. Although the precise role of gangliosides in cells remains enigmatic, the presence of specific abnormalities secondary to ganglioside accumulation in lysosomal diseases has suggested important biological functions. Chief among these is the growth of new dendrites on particular classes of mature neurons secondary to an increase in GM2 ganglioside. That GM2 has also been shown to be elevated in normal immature neurons coincident with dendritic sprouting provides a compelling argument that this ganglioside plays a role in dendritic initiation. This discovery has led to the search for other regulators of dendritic differentiation that may in some way be linked to the expression and/or function of GM2 ganglioside. Principal candidates that have emerged include tyrosine kinase receptors, small GTPases and calcium/calmodulin-dependent protein kinase II. Understanding the mechanism underlying ectopic dendritogenesis in lysosomal diseases can be expected to generate significant insight into the control of dendritic plasticity in normal brain. The detrimental aspects of ganglioside accumulation in storage diseases as well as the potential link between gangliosides and dendritogenesis also provide a strong rationale for developing pharmacological means to manipulate ganglioside expression in neurons.     

Dairy ruminant exposure to persistent organic pollutants and excretion to milk

Human activities produce polluting compounds such as persistent organic pollutants (POPs), which may interact with agriculture. These molecules have raised concern about the risk of transfer through the food chain via the animal product. POPs are characterised by a strong persistence in the environment, a high volatility and a lipophilicity, which lead to their accumulation in fat tissues. These compounds are listed in international conventions to organise the information about their potential toxicity for humans and the environment. The aim of this paper is to synthesise current information on dairy ruminant exposure to POPs and the risk of their transfer to milk. Three major groups of POPs have been considered: the polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), the polychlorobiphenyls (PCBs) and the polycyclic aromatic hydrocarbons (PAHs). The results show that contamination of fodder and soil by these compounds is observed when they are exposed to emission sources (steelworks, cementworks, waste incinerators or motorways) compared with remote areas. In general, soil contamination is considered higher than plant contamination. Highest concentrations of POPs in soil may be close to 1000 ng/kg dry matter (DM) for PCDD/Fs, to 10 000 mg/kg DM for PAHs and 100 μg/kg DM for PCBs. The contamination of milk by POPs depends on environmental factors, factors related to the rearing system (fodder and potentially contaminated soil, stage of lactation, medical state of the herd) and of the characteristics of the contaminants. Transfer rates to milk have been established: for PCBs the rate of transfer varies from 5% to 90%, for PCDD/Fs from 1% to 40% and for PAHs from 0.5% to 8%. The differential transfer of the compounds towards milk is related to the hydrophobicity of the pollutants as well as to the metabolic susceptibility of the compounds.     

Nuclear receptors in renal disease

Diabetes is the leading cause of end-stage renal disease in developed countries. In spite of excellent glucose and blood pressure control, including administration of angiotensin converting enzyme inhibitors and/or angiotensin II receptor blockers, diabetic nephropathy still develops and progresses. The development of additional protective therapeutic interventions is, therefore, a major priority. Nuclear hormone receptors regulate carbohydrate metabolism, lipid metabolism, the immune response, and inflammation. These receptors also modulate the development of fibrosis. As a result of their diverse biological effects, nuclear hormone receptors have become major pharmaceutical targets for the treatment of metabolic diseases. The increasing prevalence of diabetic nephropathy has led intense investigation into the role that nuclear hormone receptors may have in slowing or preventing the progression of renal disease. This role of nuclear hormone receptors would be associated with improvements in metabolism, the immune response, and inflammation. Several nuclear receptor activating ligands (agonists) have been shown to have a renal protective effect in the context of diabetic nephropathy. This review will discuss the evidence regarding the beneficial effects of the activation of several nuclear, especially the vitamin D receptor (VDR), farnesoid X receptor (FXR), and peroxisome-proliferator-associated receptors (PPARs) in preventing the progression of diabetic nephropathy and describe how the discovery and development of compounds that modulate the activity of nuclear hormone receptors may provide potential additional therapeutic approaches in the management of diabetic nephropathy. This article is part of a Special Issue entitled: Translating nuclear receptors from health to disease.     

Possible role for protein kinase C in the pathogenesis of inborn errors of metabolism

Protein kinase C (PKC) is a ubiquitous enzyme family implicated in the regulation of a large number of short- and long-term intracellular processes. It is hypothesized that modulation of PKC activity may represent, at least in part, a functional link between mutations (genotype) that lead to the pathological accumulation of naturally occurring compounds that affect PKC activity and perturbation of PKC-mediated substrate phosphorylation and cellular function in the corresponding diseases (phenotype). This model provides a unifying putative mechanism by which the phenotypic expression of some inborn errors of metabolism may be explained. Recent studies in a cell-free system of human skin fibroblasts support the hypothesis that alteration of PKC activity may represent the functional link between accumulation of sphingolipids and fatty acyl-CoA esters, and perturbation of cell function in sphingolipidoses and fatty acid oxidation defects, respectively. Further studies will elucidate the effects of these alterations on PKC-mediated short- and long-term cellular functions in these diseases, as well as the possible role of PKC in the pathogensis of other diseases. © 1995 Wiley-Liss, Inc.     

Activation of peroxisome proliferator-activated receptor-alpha stimulates both differentiation and fatty acid oxidation in adipocytes

Peroxisome proliferator-activated receptor-α (PPARα) is a dietary lipid sensor, whose activation results in hypolipidemic effects. In this study, we investigated whether PPARα activation affects energy metabolism in white adipose tissue (WAT). Activation of PPARα by its agonist (bezafibrate) markedly reduced adiposity in KK mice fed a high-fat diet. In 3T3-L1 adipocytes, addition of GW7647, a highly specific PPARα agonist, during adipocyte differentiation enhanced glycerol-3-phosphate dehydrogenase activity, insulin-stimulated glucose uptake, and adipogenic gene expression. However, triglyceride accumulation was not increased by PPARα activation. PPARα activation induced expression of target genes involved in FA oxidation and stimulated FA oxidation. In WAT of KK mice treated with bezafibrate, both adipogenic and FA oxidation-related genes were significantly upregulated. These changes in mRNA expression were not observed in PPARα-deficient mice. Bezafibrate treatment enhanced FA oxidation in isolated adipocytes, suppressing adipocyte hypertrophy. Chromatin immunoprecipitation (ChIP) assay revealed that PPARα was recruited to promoter regions of both adipogenic and FA oxidation-related genes in the presence of GW7647 in 3T3-L1 adipocytes. These findings indicate that the activation of PPARα affects energy metabolism in adipocytes, and PPARα activation in WAT may contribute to the clinical effects of fibrate drugs.     

Retroperitoneal white adipose tissue mitochondrial function and adiponectin expression in response to ovariectomy and 17β-estradiol replacement

Sexual dimorphism has been previously found both in mitochondrial biogenesis and function and in adiponectin expression of retroperitoneal WAT. However, little is known about the E2 effects on WAT mitochondrial function. Accordingly, the aim of this study was to examine in greater depth the role of estrogens in sexual dimorphism. This was accomplished by studying the effects of ovariectomy and E2 replacement on retroperitoneal WAT mitochondrial function. Fourteen-week-old female and ovariectomized (OVX) female Wistar rats were used in this study. The ovariectomy was performed at 5 weeks of age and at 10 weeks of age OVX rats were divided into two experimental groups: OVX, and OVX treated with 17β-estradiol (E2) (OVX+E2). Subcutaneous injections of E2 (10 μg/kg/48 h) were administered to the OVX+E2 rats for 4 weeks previous to the sacrifice whereas OVX rats were treated only with the vehicle. Levels of the main markers for mitochondrial biogenesis and function and those representatives of the antioxidant defense system and insulin sensitivity were determined. Additionally, the mRNA levels of the α and β estrogen receptors and of some adipocyte differentiation markers were studied. Our results indicate that retroperitoneal WAT was able to adapt itself to ovariectomy without any changes in mitochondrial function markers or for the adiponectin levels. However, E2 supplementation led to an unexpected decrease in: TFAM protein levels, in LPL, PPARγ and adiponectin gene expression and in the systemic HMW adiponectin levels. This decrease is probably due to the down-regulation of the ERα mRNA expression to avoid an over-stimulation by E2.     

Lipophilic Environmental Chemical Mixtures Released During Weight-Loss: The Need to Consider Dynamics

Intentional weight loss can increase health risk in the long-term, despite short-term benefits, because human adipose tissue is widely contaminated with various lipophilic environmental contaminants, especially persistent organic pollutants (POPs). Recently, chronic exposure to low POPs has emerged as a new risk factor for common metabolic diseases and cardiovascular diseases. The amount of POPs released from adipocytes to the circulation increases during weight loss, thereby increasing POPs exposure of other critical organs. Possible harmful effects due to release of POPs during weight loss are opposite to those usually expected from losing weight. It is speculated that this tradeoff can explain recent puzzling findings on intensive weight loss. The presence of POPs in adipose tissue adds a challenge to weight management and an optimal strategy of weight management needs to consider both fat mass and dynamics of POPs.     

Up-regulation of mitochondrial activity and acquirement of brown adipose tissue-like property in the white adipose tissue of fsp27 deficient mice

Fsp27, a member of the Cide family proteins, was shown to localize to lipid droplet and promote lipid storage in adipocytes. We aimed to understand the biological role of Fsp27 in regulating adipose tissue differentiation, insulin sensitivity and energy balance. Fsp27(-/-) mice and Fsp27/lep double deficient mice were generated and we examined the adiposity, whole body metabolism, BAT and WAT morphology, insulin sensitivity, mitochondrial activity, and gene expression changes in these mouse strains. Furthermore, we isolated mouse embryonic fibroblasts (MEFs) from wildtype and Fsp27(-/-) mice, followed by their differentiation into adipocytes in vitro. We found that Fsp27 is expressed in both brown adipose tissue (BAT) and white adipose tissue (WAT) and its levels were significantly elevated in the WAT and liver of leptin-deficient ob/ob mice. Fsp27(-/-) mice had increased energy expenditure, lower levels of plasma triglycerides and free fatty acids. Furthermore, Fsp27(-/-)and Fsp27/lep double-deficient mice are resistant to diet-induced obesity and display increased insulin sensitivity. Moreover, white adipocytes in Fsp27(-/-) mice have reduced triglycerides accumulation and smaller lipid droplets, while levels of mitochondrial proteins, mitochondrial size and activity are dramatically increased. We further demonstrated that BAT-specific genes and key metabolic controlling factors such as FoxC2, PPAR and PGC1alpha were all markedly upregulated. In contrast, factors inhibiting BAT differentiation such as Rb, p107 and RIP140 were down-regulated in the WAT of Fsp27(-/-) mice. Remarkably, Fsp27(-/-) MEFs differentiated in vitro show many brown adipocyte characteristics in the presence of the thyroid hormone triiodothyronine (T3). Our data thus suggest that Fsp27 acts as a novel regulator in vivo to control WAT identity, mitochondrial activity and insulin sensitivity.     

Loss of DJ-1 promotes browning of white adipose tissue in diet-induced obese mice

The seminal discovery of browning of white adipose tissue (WAT) holds great promise for the treatment of obesity and metabolic syndrome. DJ-1 is evolutionarily conserved across species, and mutations in DJ-1 have been identified in Parkinson's disease. Higher levels of DJ-1 are associated with obesity, but the underlying mechanism is less understood. Here, we report the previously unappreciated role of DJ-1 in white adipocyte biology in mature models of obesity. We used DJ-1 knockout (KO) mouse models and wild-type littermates maintained on a normal diet or high-fat diet as well as in vitro cell models to show the direct effects of DJ-1 depletion on adipocyte phenotype, thermogenic capacity, fat metabolism, and microenvironment profile. Global DJ-1 KO mice show increased sympathetic input to WAT and β3-adrenergic receptor intracellular signaling, leading to a previously unrecognized compensatory mechanism through browning of WAT with associated characteristics, including high mitochondrial contents, reduced lipid accumulation, adequate vascularization and attenuated autophagy. DJ-1 KO mice had normal body weight, energy balance, and adiposity, which were associated with protective effects on healthy WAT expansion by hyperplasia. Our findings revealed that browning of inguinal WAT occurred in DJ-1 KO mice that do not show increased predisposition to obesity and suggest that such potential mechanism may overcome the adverse metabolic consequences of obesity independent of an effect on body weight. Here, we provide the first direct evidence that targeting DJ-1 in adipocyte metabolic health may offer a unique therapeutic strategy for the treatment of obesity.     

CD44 Plays a Critical Role in Regulating Diet-Induced Adipose Inflammation,Hepatic Steatosis,and Insulin Resistance

CD44 is a multifunctional membrane receptor implicated in the regulation of several biological processes, including inflammation. CD44 expression is elevated in liver and white adipose tissue (WAT) during obesity suggesting a possible regulatory role for CD44 in metabolic syndrome. To study this hypothesis, we examined the effect of the loss of CD44 expression on the development of various features of metabolic syndrome using CD44 null mice. Our study demonstrates that CD44-deficient mice (CD44KO) exhibit a significantly reduced susceptibility to the development of high fat-diet (HFD)-induced hepatic steatosis, WAT-associated inflammation, and insulin resistance. The decreased expression of genes involved in fatty acid synthesis and transport (Fasn and Cd36), de novo triglyceride synthesis (Mogat1), and triglyceride accumulation (Cidea, Cidec) appears in part responsible for the reduced hepatic lipid accumulation in CD44KO(HFD) mice. In addition, the expression of various inflammatory and cell matrix genes, including several chemokines and its receptors, osteopontin, and several matrix metalloproteinases and collagen genes was greatly diminished in CD44KO(HFD) liver consistent with reduced inflammation and fibrogenesis. In contrast, lipid accumulation was significantly increased in CD44KO(HFD) WAT, whereas inflammation as indicated by the reduced infiltration of macrophages and expression of macrophage marker genes, was significantly diminished in WAT of CD44KO(HFD) mice compared to WT(HFD) mice. CD44KO(HFD) mice remained considerably more insulin sensitive and glucose tolerant than WT(HFD) mice and exhibited lower blood insulin levels. Our study indicates that CD44 plays a critical role in regulating several aspects of metabolic syndrome and may provide a new therapeutic target in the management of insulin resistance.     

Are cockroaches reliable bioindicators of persistent organic pollutant contamination of indoor environments?

We measured the concentrations of selected persistent organic pollutants (POPs) such as parent and halogenated polycyclic aromatic hydrocarbons (PAHs and HPAHs) and polybrominated diphenyl ethers (PBDEs) in indoor dust (ID) and indoor cockroach samples collected from Shenzhen, South China. Biota-dust accumulation factors (BDAFs) were computed and utilized to quantify targeted pollutant bioaccumulation in ID and cockroaches. Generally, halogenated compounds have higher BDAFs when compared to non-halogenated compounds. There are significant differences (p < 0.05) between the BDAFs of non-halogenated POPs (PAHs) and halogenated POPs (HPAHs and PBDEs). Correlation analysis of target pollutants’ levels in ID and cockroaches were also conducted. The correlation coefficients for PAHs are less than 0.2 (p > 0.5) suggesting no significant relationship exists for PAHs between ID and cockroaches. In contrast, significant correlations exist for halogenated POPs (HPAH and PBDE) between ID and cockroaches (correlation coefficients >0.94, p < 0.0001). Based on this, the potential of cockroaches to be used as reliable bioindicators of POPs contamination of indoor environments was preliminarily evaluated. Our results indicate that indoor cockroaches may be useful bioindicator of indoor pollution for HPAHs and PBDEs contaminations.     

Plant sterol oxidation products – Analogs to cholesterol oxidation products from plant origin?

Cholesterol and plant sterols are lipids which are abundantly present in a western type diet of animal and plant origin, respectively. The daily intake averages 300 mg/day each. Over the past decades, a steadily increasing consumption of plant sterol enriched dairy products (2–3 g/day) took place to lower circulating LDL cholesterol concentrations. Like all unsaturated components, plant sterols can be attacked by reactive oxygen species resulting in plant sterol oxidation products (POPs). The most widespread methods for POP determination are high-performance liquid chromatography and gas–liquid chromatography. Yet, based on the low plasma POP concentrations in normophytosterolemic subjects (POPs: ∼0.3–4.5 ng/mL), a reliable quantification yielding an appropriate limit of detection remains a challenge. While the more abundantly present cholesterol oxidation products (COPs) have elaborately been studied, research on the metabolism and biological effects of POPs is only emerging. In relation to atherogenity, biological effects including modulation of cholesterol homeostasis, membrane functioning, and inflammation are attributed to POPs. Although mostly supra-physiological concentrations are applied in in vitro assays, anti-tumor activity, cytotoxicity and estrogen-competition have been attributed to specific POPs. However, it is not obvious, if and how POPs may exert in vivo adverse or beneficial health effects similar to those attributed to COPs. In the field of nutritional science, standardized methods for the determination of POPs are required to perform relevant biological studies and to assess their presence in complex foods or biological tissues and fluids. The aim of this review is to provide an overview and evaluation of the published methods and an update on the biological effects attributed to POPs.     

Protein kinase Cβ deficiency attenuates obesity syndrome of ob/ob mice by promoting white adipose tissue remodeling

To explore the role of leptin in PKCβ action and to determine the protective potential of PKCβ deficiency on profound obesity, double knockout (DBKO) mice lacking PKCβ and ob genes were created, and key parameters of metabolism and body composition were studied. DBKO mice had similar caloric intake as ob/ob mice but showed significantly reduced body fat content, improved glucose metabolism, and elevated body temperature. DBKO mice were resistant to high-fat diet-induced obesity. Moreover, PKCβ deficiency increased β-adrenergic signaling by inducing expression of β1- and β3-adrenergic receptors (β-ARs) in white adipose tissue (WAT) of ob/ob mice. Accordingly, p38(MAPK) activation and expression of PGC-1α and UCP-1 were increased in WAT of DBKO mice. Consistent with results of in vivo studies, inhibition of PKCβ in WAT explants from ob/ob mice also increased expression of above β-ARs. In contrast, induction of PGC-1α and UCP-1 expression in brown adipose tissue of DBKO mice was not accompanied by changes in the expression of these β-ARs. Collectively, these findings suggest that PKCβ deficiency may prevent genetic obesity, in part, by remodeling the catabolic function of adipose tissues through β-ARs dependent and independent mechanisms.     

Pterostilbene,a dimethylated analog of resveratrol,promotes energy metabolism in obese rats

Pterostilbene (trans-3,5-dimethoxy-4-hydroxystilbene) is a dimethylated analog of resveratrol and has been reported to exert various pharmacological effects. In this study, we evaluated the effect of pterostilbene on the pathogenesis of obesity and energy metabolism in obese rats.Pterostilbene significantly activates silent mating type information regulation 2 homolog-1 and peroxisome proliferator-activated receptor-alpha in vitro. At 4 weeks a 0.5% pterostilbene diet markedly suppressed the abdominal white adipose tissue (WAT) accumulation in obese rats. The oxygen consumption and energy expenditure were significantly higher in the pterostilbene group, and pterostilbene increased the fat metabolism rather than the carbohydrate metabolism in obese rats. The mRNA level of uncoupling protein, a thermogenic regulator, was increased and the mRNA levels of fatty acid synthase and leptin, which are involved in lipogenesis and fat storage, were markedly decreased in WAT after the pterostilbene feeding. These results suggest that pterostilbene prevents WAT accumulation through the enhancement of energy metabolism and partly the suppression of lipogenesis in obese OLETF rats.     

Stimulation of mitochondrial oxidative capacity in white fat independent of UCP1: A key to lean phenotype

We are facing a revival of the strategy to counteract obesity and associated metabolic disorders by inducing thermogenesis mediated by mitochondrial uncoupling protein-1 (UCP1). Thus, the main focus is on the adaptive non-shivering thermogenesis occurring both in the typical depots of brown adipose tissue (BAT) and in UCP1-containing cells that could be induced in white adipose tissue (WAT). Because contribution of WAT to resting metabolic rate is relatively small, the possibility to reduce adiposity by enhancing energy expenditure in classical white adipocytes is largely neglected. However, several pieces of evidence support a notion that induction of energy expenditure based on oxidation of fatty acids (FA) in WAT may be beneficial for health, namely: (i) studies in both humans and rodents document negative association between oxidative capacity of mitochondria in WAT and obesity; (ii) pharmacological activation of AMPK in rats as well as cold-acclimation of UCP1-ablated mice results in obesity resistance associated with increased oxidative capacity in WAT; and (iii) combined intervention using long-chain n-3 polyunsaturated FA (omega 3) and mild calorie restriction exerted synergism in the prevention of obesity in mice fed a high-fat diet; this was associated with strong hypolipidemic and insulin-sensitizing effects, as well as prevention of inflammation, and synergistic induction of mitochondrial oxidative phosphorylation (OXPHOS) and FA oxidation, specifically in epididymal WAT. Importantly, these changes occurred without induction of UCP1 and suggested the involvement of: (i) futile substrate cycle in white adipocytes, which is based on lipolysis of intracellular triacylglycerols and re-esterification of FA, in association with the induction of mitochondrial OXPHOS capacity, β-oxidation, and energy expenditure; (ii) endogenous lipid mediators (namely endocannabinoids, eicosanoids, prostanoids, resolvins, and protectins) and their cognate receptors; and (iii) AMP-activated protein kinase in WAT. Quantitatively, the strong induction of FA oxidation in WAT in response to the combined intervention is similar to that observed in the transgenic mice rendered resistant to obesity by ectopic expression of UCP1 in WAT. The induction of UCP1-independent FA oxidation and energy expenditure in WAT in response to the above physiological stimuli could underlie the amelioration of obesity and low-grade WAT inflammation, and it could reduce the release of FA from adipose tissue and counteract harmful consequences of lipid accumulation in other tissues. In this respect, new combination treatments may be designed using naturally occurring micronutrients (e.g. omega 3), reduced calorie intake or pharmaceuticals, exerting synergism in the induction of the mitochondrial OXPHOS capacity and stimulation of lipid catabolism in white adipocytes, and improving metabolic flexibility of WAT. The role of mutual interactions between adipocytes and immune cells contained in WAT in tissue metabolism should be better characterised. This article is part of a Special Issue entitled Brown and White Fat: From Signaling to Disease.     

Hypoxia-mimetic effects in the secretome of human preadipocytes and adipocytes

White adipose tissue (WAT) regulates energy metabolism by secretion of proteins with endocrine and paracrine effects. Dysregulation of the secretome of obesity-associated enlarged WAT may lead to obesity-related disorders. This can be caused by hypoxia as a result of poorly vascularized WAT. The effect of hypoxia on the secretome of human (pre)adipocytes is largely unknown. Therefore, we investigated the effect of CoCl₂, a hypoxia mimetic, on the secretome of human SGBS (pre)adipocytes by a proteomics approach combined with bioinformatic analysis. In addition, regulation of protein secretion was examined by protein turnover experiments. As such, secretome changes were particularly associated with protein down-regulation and extracellular matrix protein dysregulation. The observed up-regulation of collagens in adipocytes may be essential for cell survival while down-regulation of collagens in preadipocytes may indicate a disturbed differentiation process. These CoCl₂-induced changes reflect WAT dysfunction that ultimately may lead to obesity-associated complications. In addition, 9 novel adipocyte secreted proteins were identified from which 6 were regulated by CoCl₂. Mass spectrometry data have been deposited to the ProteomeXchange with identifier PXD000162.